Wednesday, July 28, 2010

University of southern California researchers show us a more successful use of graphene photovoltaics

Could you imagine people powering their cellular phone or music/video device while jogging on a sunny day?

A University of Southern California team has produced flexible transparent carbon atom films that may have great potential for a new variety of solar cells.

Inside a paper recently published by the journal ACS Nano, researchers stated that organic photovoltaic (OPV) cells have been proposed as an approach to get cost effective energy due to their ease of manufacture, light-weight, and compatibility with flexible substrates.

The new work suggests that graphene, a highly conductive and highly transparent type of carbon consisting of atoms-thick sheets of carbon atoms, has high potential to fill this role.

While graphene’s existence has been known for many years, it has only been studied extensively since 2004 due to the difficulty of manufacturing it in high quality and in quantity.

The University of southern California team has produced graphene/polymer sheets ranging in sizes up to 150 square centimeters that in turn can be used to create dense arrays of flexible organic photovoltaic (OPV) cells.

These organic photovoltaic (OPV) devices convert solar radiation to electricity, but not as efficiently as silicon cells.

The energy provided by sunlight on a sunny day is approximately 1,000 watts per meter square, for every 1,000 watts of sunlight that hits a square meter area of the standard silicon solar cell, 14 watts of electricity will be generated, Organic solar cells are less efficient; their conversion rate for that same 1,000 watts of sunlight in the graphene-based solar cell could be only 1.3 watts.

But what graphene organic photovoltaic (OPV) lack in efficiency, can potentially be compensated by its lower price and, greater physical flexibility.

Researchers think that it may eventually be possible to cover with inexpensive solar cell layers extensive areas like newspapers, magazines or power generating clothing.

In the meanwhile Prof. Ruoff and his colleagues of the mechanical engineering department at the University of Texas at Austin, are studying the basic science in the development of graphene-based ultracapacitors for usage in electronics and various fields.

Prof. Ruoff says batteries are relatively slow, they can store energy but require sometime to charge up, and then they distribute energy slowly, over time.

Ultracapacitors can be charged rapidly, within seconds, and discharge in a short time, but, today, they’re not able to store very much electrical energy.

The introduction of stable and less expensive ultracapacitors could be a key step in using wind or solar-generated power, specially if researchers can discover methods to enable capacitors to store energy longer, that is not yet possible.

Even with their current storage capacity, the graphene devices could provide quick energy when needed in certain situations on the environmentally friendly way.

They could be used, for example, to absorb the heat generated in braking a car or train, and store it for a short time, and then use it for the electrical needs of the vehicle (i.e. starting the car or acceleration)

About the Author – Sophia H. Walker writes for the solar powered battery charger blog, her personal hobby site devoted to tips to help people save electricity using solar powered energy for small accessories.